Ricin is one of the most potent biological toxins known and has been used as a biological weapon in the past. Much attention has been recently focused on the potential threat of actual ricin use, since traces of ricin have been found and documented in several well publicized incidents during 2003. Currently, there is no licensed vaccine to protect against the possibility of the aerosol use of ricin in a potential terrorist attack or as a weapon on the battlefield. The purpose of this proposed project is to develop an intramuscularly administered ricin vaccine through process and intermediate scale-up stages of manufacturing, up to and including formulation with adjuvant in vials for final release for human clinical studies. The team for this project includes representatives from industry (DOR Biopharmaceuticals, Inc. [DOR] and Cambrex Biosciences, Inc. [CAMB]), academe (University of Texas Southwestern Medical Center [UTSWMC] and the University of Kansas [UK]) and a non-profit research organization (Stanford Research Institute [SRI]). A production goal of at least several thousand human doses sufficient for stability and toxicity testing, in addition to future Phase I/II clinical testing, is projected. The vaccine candidate is a recombinant polypeptide derived from the A chain of ricin toxin produced in an E. coli host strain. The proposed efforts will focus on the development of a previously characterized genetically inactivated ricin A chain that contains non-redundant structural mutations in sites resulting in loss of toxicity. The activities involved in executing the specific aims will include maximization of expression levels in E. coli, improvement of process yields, and development and validation of process methods, assays, and stability-indicating tests. Several factors that contribute to the stability of the antigen in solution will be addressed in formulating the vaccine for clinical use. Further, the developed lots will be tested in animal models for efficacy and potential toxicity issues will be addressed. A key issue in the development of a vaccine to combat ricin intoxication will be the correlation of animal protective responses with human protective responses, since no human challenge/efficacy studies can be performed during development. Based on preliminary data, this particular vaccine antigen aggregates under certain conditions, potentially affecting potency and stability. Preservation of the polypeptide structure during storage of the vaccine will also be addressed by formulating the vaccine candidate in protein stabilizinq recipients. [unreadable] [unreadable]